From early ‘90s, various isotopic techniques demonstrated the presence of CYP19A1, 17βHSD reductive/oxidative, 3βHSD and STS activities and the mRNA expression of 17βHSD1, 2, 4, STS, SULT1E1, CYP19A1 and SDR5A in human osteoblastic (e.g., HOS, U20S, HTB-96 and MG63) and osteosarcoma cell lines like CRL-1543 (Purohit et al., 1992; Fujikawa et al., 1997; Jakob et al., 1997; Dong et al., 1998; Saito and Yanaihara, 1998; Janssen et al., 1999; Muir et al., 2004; Svoboda et al., 2007; Dias and Selcer, 2014). This evidence concerns the gene CYP19A1 and osteosarcoma.